Low idle and unbalanced carbs will make this chatter noise more pronounced.
The noise is caused by the uneven load on some of the free spinning gears on the output shaft as this shaft is standing still when the bike is parked. The other two shafts is spinning till you pull the clutch and then they will also come to a standstill and that is why the noise will stop.
Do not concern yourself with this, it is not even an indication that the gears is worn or loose as a brand new gearbox will also make similar noises.

Low idle and unbalanced carbs will make this chatter noise more pronounced.
The noise is caused by the uneven load on some of the free spinning gears on the output shaft as this shaft is standing still when the bike is parked. The other two shafts is spinning till you pull the clutch and then they will also come to a standstill and that is why the noise will stop.
Do not concern yourself with this, it is not even an indication that the gears is worn or loose as a brand new gearbox will also make similar noises.

Click to expand...

That's a really good answer. Thank you as I have the same noise. Pull clutch in lovely and quiet, let it out, chatter, chatter!